English: Pre- and post-central gyrus, right hemisphere. Microstructural 7-T MR mapping in post-mortem brains. (A) Tissue block (pre- and post-central gyrus, right hemisphere) from a post-mortem human brain (female, 61 years, died of pulmonary failure and chronic obstructive pulmonary disease, autopsy performed with informed consent of the patient’s relatives, post-mortem interval before fixation 24 h, fixed in 4% formalin for 2 months) prior to MR scanning and histological processing. M1 = primary motor cortex in the posterior wall of the precentral gyrus, S1 = primary somatosensory cortex in the anterior wall of the post-central gyrus. (B) Quantitative T1 map of the tissue block [for plane of sectioning see rectangle in (A)]. MP2RAGE sequence at 7 T, voxel size (0.33 mm)3, 32 averages, acquisition time 3 h 50 min, surrounding medium: Fomblin (Solvay Solexis, Bollate, Italy). Arrow indicates a sharp change in T1 contrast at the base of the precentral gyrus that matches a change in the myelo- and cytoarchitectonic pattern [cf. (C,D)]. (C,D) Frozen sections (30 μm) from a corresponding position of the same block stained for myelin basic protein [rat monoclonal antibody, avidin–biotin–peroxidase complex (ABC) method, chromogen: DAB and ammonium nickel(II) sulfate (C)] and cell bodies. Micrographs show the fundus of the central sulcus [same orientation as in (A,B)]. The drop in T1 values at the base of the precentral gyrus coincides with an increase in myelin basic protein immunostaining [line in (C)]. In an accompanying section stained for cell bodies, this position is characterized by an increase in gray matter thickness, a disappearing inner granular layer (asterisks), and emerging giant pyramidal (Betz) cells (arrowheads). This transition [lines in (C,D)] corresponds to the border between area 3a (somatosensory cortex) and area 4 (primary motor cortex).